A technique disclosed herein relates to a landing gear retraction/extension device of an aircraft including an electro hydrostatic actuator (EHA) system.
In a technical field of automobiles, a technique has been known, in which various oil temperatures are maintained at equal to or higher than a predetermined temperature during traveling of a vehicle, and therefore oil viscosity is maintained at equal to or less than a predetermined value.
For example, Japanese Patent Publication No. 2008-273361 describes an electric hydraulic power steering device including an electric motor and a hydraulic pump driven by the electric motor. In the electric hydraulic power steering device, operation oil is heated by using heat from the electric motor, and the temperature of the operation oil is maintained at a predetermined temperature. In addition, in the electric hydraulic power steering device, when an operation oil temperature of equal to or lower than the predetermined temperature, and the power steering device is not substantially operated because steering force caused by steering device is equal to or less than a required force, current which is not capable of rotating the electric motor is applied to the electric motor to generate heat, thereby heating operation oil.
Japanese Patent Publication No. 2005-348535, Japanese Patent Publication No. 2002-161966, and Japanese Patent Publication No. 2003-339101 each describe a hybrid electric vehicle (HEV) including an engine and a drive motor or an electric vehicle (EV) including a drive motor. In the HEV or the EV, cooling oil and/or automatic transmission fluid and/or lubrication oil for a differential gear is maintained at a predetermined temperature during traveling of the vehicle by using liberated heat energy by driving motor.
Japanese Patent Publication No. 2000-014114 describes a disk device for, e.g., CDs and DVDs, and the disk device includes a motor having an oil-containing bearing. In the disk device, upon low-temperature start-up, current is supplied to a coil of the motor to generate heat in the coil, and then lubrication oil of the bearing is heated. In such a manner, it is ensured that the motor is started in a short time.
Japanese Patent Publication No. 2004-162860 describes a hydraulic drive device such as machine tools. In the hydraulic drive device, when an operation oil temperature is equal to or lower than a predetermined value upon start-up of the hydraulic drive device, current which has a non-optimal phase for driving motor is supplied to an electric motor to increase the amount of heat generation at an electric coil. In such a manner, the operation oil temperature is quickly increased.